Flexible Shipping doesn’t recognize translated product categories. Therefore, if your multilingual website has product categories translated into languages other than the site’s default language, the plugin won’t detect them. Because of this, it’s best to avoid using shipping rules based on product categories in such cases.
Solution:
The best way to address this issue is to base your shipping rules on shipping classes instead. So, instead of using a setup like this:
You can, for example, use a setup like this:
